Asynchronous Transfer Mode (ATM) is a high-speed connection-oriented multiplexing and switching method specified in international standards utilizing fixed-length cells to support multiple types of traffic. ATM has become a popular solution for digital broadcast signals transmitted over transmission mediums using the Synchronous Optical Network (SONET) and the Synchronous Digital Hierarchy (SDH) transport standard. The SONET transport standard has traditionally supported data transmission at frequencies of 1.5, 6, 45, and 140 megabits per second (MB/s). The SDH transport standard has traditionally supported data transmission at frequencies of 2, 8, 34, and 140 MB/s.
ATM allows data streams with varying bit rates to be effectively mapped onto transmission mediums using the SONET and SDH transport standards. ATM segments a data stream and writes the segmented data stream into payload sections of ATM cells that are transmitted on the transmission medium. ATM varies the density of the data written into each ATM cell which allows the data stream to be transmitted on the transmission medium at the appropriate rate.
One drawback of the ATM solution is that it may be expensive to implement. The ATM solution requires a complex network management system to support its switched network, multi-path environment. In addition, when transmitting large amounts of data, the data is required to be segmented into many small ATM cells no larger than 53 bytes which translates to additional overhead which is undesirable. Data transmission applications such as digital broadcasts are single-path, uni-direction applications that require large amounts of data to be transmitted. Digital broadcast applications that implement ATM do not utilize all the functionalities of ATM while incurring many of its drawbacks.
Thus, a more efficient method and apparatus for dynamically allocating bandwidth to data with varying bit rates is needed.